Systems and methods for idle fuel economy mode

ABSTRACT

An apparatus includes a stored reductant determination circuit structured to determine an amount of stored reductant in a component of an exhaust aftertreatment system, and a fuel mode economy circuit structured to control an amount of reductant added to the exhaust aftertreatment system during an engine idle mode of operation based on the amount of stored reductant.

TECHNICAL FIELD

The present disclosure relates to exhaust aftertreatment systems. Moreparticularly, the present disclosure relates to operating an in-useselective catalytic reduction and ammonia oxidation system, and anexhaust gas recirculation system of an exhaust aftertreatment system.

BACKGROUND

Emission regulations for internal combustion engines have become morestringent over recent years. Environmental concerns have motivated theimplementation of stricter emission requirements for internal combustionengines throughout much of the world. Governmental agencies, such as theEnvironmental Protection Agency (EPA) in the United States, carefullymonitor the emission quality of engines and set acceptable emissionstandards, to which all engines must comply. For example, the CaliforniaAir Board (CAB) dictates a nitrogen oxide (NOx) emission standard (e.g.,30 grams NOx per hour). Consequently, using exhaust aftertreatmentsystems to reduce engine emissions is desirable.

Exhaust aftertreatment systems can include exhaust gas recirculation(EGR) systems that recirculate exhaust gases to an intake manifold of anengine. Additionally, exhaust aftertreatment systems can includereductant dosing systems that introduce a reductant (e.g., urea, dieselexhaust fluid (DEF), ammonia solutions, etc.) to reduce the NOx thatpasses through a catalyst chamber of the aftertreatment system.

SUMMARY

One embodiment relates to an apparatus that includes a stored reductantdetermination circuit and a fuel mode economy circuit. The storedreductant determination circuit is structured to determine an amount ofstored reductant in a component of an exhaust aftertreatment system. Thefuel mode economy circuit is structured to control an amount ofreductant added to the exhaust aftertreatment system during an engineidle mode of operation based on the amount of stored reductant.

Another embodiment relates to a system that includes an exhaustaftertreatment system and a controller in communication with the exhaustaftertreatment system. The exhaust aftertreatment system including areductant source and a selective catalytic reduction (SCR) component.The controller is structured to determine an amount of stored reductantin the SCR component of the exhaust aftertreatment system, and controlan amount of reductant added to the exhaust aftertreatment system duringan engine idle mode of operation based on the amount of storedreductant.

Another embodiment relates to a method. The method includes detecting alevel of nitrogen oxide present in a flow of exhaust gas downstream of acatalyst during an engine idle mode of operation, comparing the detectedlevel of nitrogen oxide to a threshold, inhibiting a flow of reductantto the catalyst when the nitrogen oxide level is below the threshold,and providing reductant to the catalyst when the nitrogen oxide level isabove the threshold.

These and other features, together with the organization and manner ofoperation thereof, will become apparent from the following detaileddescription when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is schematic diagram of an exhaust aftertreatment system with acontroller, according to an example embodiment.

FIG. 2 is a schematic of the controller used with the system of FIG. 1,according to an example embodiment.

FIG. 3 is a flow diagram of a method of operating an engine system,according to an example embodiment.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and implementations of, methods, apparatuses, and systemsfor operating an engine in a fuel efficient idle mode. The variousconcepts introduced above and discussed in greater detail below may beimplemented in any number of ways, as the concepts described are notlimited to any particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

Referring the Figures generally, the various embodiments disclosedherein relate to systems, apparatuses, and methods for operating anengine in a fuel efficient idle mode based on an amount of reductantstored in the system. The system includes a controller and an exhaustgas aftertreatment system that includes a selective catalytic reduction(SCR) system structured to introduce or dose a reductant into an exhaustgas stream, and an exhaust gas recirculation (EGR) system. Thecontroller is structured to identify when a level of ammonia in the SCRsystem is adequate to control nitrogen oxide (NOx) emissions from theexhaust gas aftertreatment system to be below an emission thresholdwithout having to add additional reductant or without having to use EGR.If the level of ammonia is adequate to limit emissions below a desiredlevel, the controller is structured to operate the engine according tothe fuel efficient idle mode while adding substantially zero reductantto the exhaust gas stream. The controller continually monitors NOxemissions and other factors to determine when reductant dosing and/orEGR are needed and exits the fuel efficient idle mode when predeterminedconditions are met. By operating in the fuel efficient idle mode, theengine realizes substantial fuel savings while still meeting allrequired emissions standards.

As shown in FIG. 1, a schematic diagram of an exhaust aftertreatmentsystem with a controller 100 is shown according to an exampleembodiment. The engine-exhaust aftertreatment system is shown in theform of an engine system 10 that includes an internal combustion engine20 and an exhaust aftertreatment system 22 in exhaust gas-receivingcommunication with the engine 20. According to one embodiment, theengine 20 is structured as a compression-ignition internal combustionengine that utilizes diesel fuel. In various other embodiments, theengine 20 may be structured as any other type of engine (e.g.,spark-ignition, electric) that utilizes any type of fuel (e.g.,gasoline, electricity, hydrogen). Within the internal combustion engine20, air from the atmosphere is combined with fuel and combusted to powerthe engine. Combustion of the fuel and air in the compression chambersof the engine 20 produces exhaust gas that is operatively vented to anexhaust manifold (not shown) and to the aftertreatment system 22.

The exhaust aftertreatment system 22 includes a diesel particular filter(DPF) 40, a diesel oxidation catalyst (DOC) 30, a selective catalyticreduction (SCR) system 52 with an SCR catalyst 50, an ammonia oxidation(AMOx) catalyst 60, and an exhaust gas recirculation (EGR) system 70.The SCR system 52 further includes a reductant delivery system that hasa diesel exhaust fluid (DEF) source 54 that supplies DEF to a DEF doser56 via a DEF line 58.

In an exhaust flow direction, as indicated by directional arrow 29,exhaust gas flows from the engine 20 into inlet piping 24 of the exhaustaftertreatment system 22. From the inlet piping 24, the exhaust gasflows into the DOC 30 and exits the DOC into a first section of exhaustpiping 28A. From the first section of exhaust piping 28A, the exhaustgas flows into the DPF 40 and exits the DPF into a second section ofexhaust piping 28B. From the second section of exhaust piping 28B, theexhaust gas flows into the SCR catalyst 50 and exits the SCR catalystinto the third section of exhaust piping 28C. As the exhaust gas flowsthrough the second section of exhaust piping 28B, it is periodicallydosed with DEF by the DEF doser 56. Accordingly, the second section ofexhaust piping 28B acts as a decomposition chamber or tube to facilitatethe decomposition of the DEF to ammonia. From the third section ofexhaust piping 28C, the exhaust gas flows into the AMOx catalyst 60 andexits the AMOx catalyst into outlet piping 26 before the exhaust gas isexpelled from the system 22. Based on the foregoing, in the illustratedembodiment, the DOC 30 is positioned upstream of the DPF 40 and the SCRcatalyst 50, and the SCR catalyst 50 is positioned downstream of the DPF40 and upstream of the AMOx catalyst 60. However, in alternativeembodiments, other arrangements of the components of the exhaustaftertreatment system 22 are also possible.

The DOC 30 may be structured to have any number of different types offlow-through designs. Generally, the DOC 30 is structured to oxidize atleast some particulate matter in the exhaust (e.g., the soluble organicfraction of soot) and reduce unburned hydrocarbons and CO in the exhaustto less environmentally harmful compounds. For example, the DOC 30 maybe structured to reduce the hydrocarbon and CO concentrations in theexhaust to meet the requisite emissions standards for those componentsof the exhaust gas. An indirect consequence of the oxidationcapabilities of the DOC 30 is the ability of the DOC to oxidize NO intoNO₂. In this manner, the level of NO₂ exiting the DOC 30 is equal to theNO₂ in the exhaust gas generated by the engine 20 in addition to the NO₂converted from NO by the DOC.

In addition to treating the hydrocarbon and CO concentrations in theexhaust gas, the DOC 30 may also be used in the controlled regenerationof the DPF 40, SCR catalyst 50, and AMOx catalyst 60. This can beaccomplished through the injection, or dosing, of unburned HC into theexhaust gas upstream of the DOC 30. Upon contact with the DOC 30, theunburned HC undergoes an exothermic oxidation reaction which leads to anincrease in the temperature of the exhaust gas exiting the DOC 30 andsubsequently entering the DPF 40, SCR catalyst 50, and/or the AMOxcatalyst 60. The amount of unburned HC added to the exhaust gas isselected to achieve the desired temperature increase or targetcontrolled regeneration temperature.

The DPF 40 may be any of various flow-through designs, and is structuredto reduce particulate matter concentrations (e.g., soot and ash) in theexhaust gas to meet requisite emission standards. The DPF 40 capturesparticulate matter and other constituents, and thus can be periodicallyregenerated to burn off the captured constituents. Additionally, the DPF40 may be structured to oxidize NO to form NO₂ independent of the DOC30.

As discussed above, the SCR system 52 includes a reductant deliverysystem with a reductant (e.g., DEF) source 54, pump (not shown), anddelivery mechanism or doser 56. The reductant source 54 can be acontainer or tank capable of retaining a reductant, such as, forexample, ammonia (NH₃), DEF (e.g., urea), or diesel oil. The reductantsource 54 is in reductant supplying communication with the pump, whichis structured to pump reductant from the reductant source 54 to thedelivery mechanism 56 via a reductant delivery line 58. The deliverymechanism 56 is positioned upstream of the SCR catalyst 50. The deliverymechanism 56 is selectively controllable to inject reductant directlyinto the exhaust gas stream prior to entering the SCR catalyst 50. Asdescribed herein, the controller 100 is structured to control the timingand amount of the reductant delivered to the exhaust gas. In someembodiments, the reductant may either be ammonia or DEF, either of whichdecomposes to produce ammonia. As briefly described above, the ammoniareacts with NOx in the presence of the SCR catalyst 50 to reduce the NOxto less harmful emissions, such as N₂ and H₂O. The NOx in the exhaustgas stream includes NO₂ and NO. Generally, both NO₂ and NO are reducedto N₂ and H₂O through various chemical reactions driven by the catalyticelements of the SCR catalyst in the presence of NH₃.

The SCR catalyst 50 may be any of various catalysts known in the art.For example, in some implementations, the SCR catalyst 50 is avanadium-based catalyst, and in other implementations, the SCR catalystis a zeolite-based catalyst, such as a Cu-Zeolite or a Fe-Zeolitecatalyst. In one representative embodiment, the reductant is aqueousurea and the SCR catalyst 50 is a zeolite-based catalyst. In otherembodiments, the reductant includes a first reductant and a secondreductant, wherein the first reductant is urea and the second reductantis ammonia.

The AMOx catalyst 60 may be any of various flow-through catalystsstructured to react with ammonia to produce mainly nitrogen. As brieflydescribed above, the AMOx catalyst 60 is structured to remove ammoniathat has slipped through or exited the SCR catalyst 50 without reactingwith NO_(x) in the exhaust. In certain instances, the aftertreatmentsystem 22 can be operable with or without an AMOx catalyst. Further,although the AMOx catalyst 60 is shown as a separate unit from the SCRsystem 52 in FIGS. 1-2, in some implementations, the AMOx catalyst maybe integrated with the SCR catalyst (e.g., the AMOx catalyst and the SCRcatalyst can be located within the same housing). In some embodiments,the SCR catalyst and AMOx catalyst are positioned serially with the SCRcatalyst preceding the AMOx catalyst as shown in FIG. 2.

As referred to herein, the SCR catalyst 50 and AMOx catalyst 60 form theSCR and AMOx system. Accordingly, health or degradations determined arein regard to those catalysts.

Various sensors, such as NOx sensors 12, 14, 55, 57 and temperaturesensors 16, 18, may be strategically disposed throughout the exhaustaftertreatment system 22 and may be in communication with the controller100 and structured to monitor operating conditions of the engine system10. As shown, more than one NOx sensor may be positioned upstream anddownstream of the SCR catalyst 50. In this configuration, the NOx sensor12 measures the engine out NOx while NOx sensor 55 measures the SCRcatalyst 50 inlet NOx amount. This is due to DOC 30/DPF 40 potentiallyoxidizing some portion of the engine out NOx whereby the engine out NOxamount would not be equal to the SCR catalyst 50 inlet NOx amount.Accordingly, this configuration accounts for this potential discrepancy.The NOx amount leaving the SCR catalyst 50 may be measured by NOx sensor57 and/or NOx sensor 14. In some embodiments, there may be only one suchsensor, such as either one of either NOx sensor 57 or NOx sensor 14. TheNOx sensor 57 (in some embodiments, NOx sensor 14) is positioneddownstream of the SCR catalyst 50 and structured to detect theconcentration of NOx in the exhaust gas downstream of the SCR catalyst(e.g., exiting the SCR catalyst).

The temperature sensors 16 are associated with the DOC 30 and DPF 40,and thus can be defined as DOC/DPF temperature sensors 16. The DOC/DPFtemperature sensors are strategically positioned to detect thetemperature of exhaust gas flowing into the DOC 30, out of the DOC andinto the DPF 40, and out of the DPF before being dosed with DEF by thedoser 56. The temperature sensors 18 are associated with the SCRcatalyst 50 and thus can be defined as SCR temperature sensors 18. TheSCR temperature sensors 18 are strategically positioned to detect thetemperature of exhaust gas flowing into and out of the SCR catalyst 50.

The EGR system 70 is structured to recirculate exhaust gas back to anintake manifold of the engine 20 to be re-used for combustion. Byrouting exhaust gas back to the engine 20 for combustion, inert gasesare provided for combustion and function to absorb combustion heat toreduce peak in-cylinder temperatures. Advantageously, this functionworks to reduce nitrous oxide (NOx) emissions from the engine 20. Asshown, the EGR system 70 includes an EGR orifice 72, an EGR cooler 74,and an EGR valve 76. It should be understood that this diagram is anexample only and not meant to be limiting as many other components maybe added or excluded from the EGR system 70 (as well as the enginesystem 10 in general). For example, the EGR orifice 72 is an optionalcomponent as is the EGR cooler 74, as some configurations may notinclude these components. The EGR valve 76 is selectively activated bythe controller 100 and includes any type of valve typically includedwith EGR systems. When the EGR valve 76 is fully closed, exhaust gas isinhibited from recirculating back to the intake manifold 21. When theEGR valve 76 is fully or partially open, exhaust gas is permitted torecirculate back to the intake manifold 21. The EGR orifice 72 isstructured as any type of EGR orifice typically included in EGR systems.The EGR orifice 72 is situated between an exhaust manifold of the engine20 and the EGR valve 76. Due to this positioning, a pressure drop isformed across the EGR orifice 72 whenever exhaust gas is recirculated tothe intake manifold (e.g., the EGR valve 76 is open or partially open).Temperature sensors, pressure sensors, and/or flow sensors may bepositioned proximate the EGR orifice 72 and may be communicably coupledto the controller 100 and structured to acquire and provide dataindicative of a temperature, pressure, and flow of exhaust gas flowingthrough the EGR orifice 72 in the EGR system 70 toward the intakemanifold.

As mentioned above, the EGR system 70 includes an EGR cooler 74 and anEGR valve 76. The EGR cooler 74 is structured as any type of heatexchanger typically included in EGR systems including, but not limitedto, air-to-air and/or liquid (e.g., coolant)-to-air (e.g., exhaust gas)heat exchangers. The EGR cooler 74 is structured to remove heat from theexhaust gas prior to the exhaust gas being re-introduced into the intakemanifold. Heat is removed from the exhaust gas prior to reintroductionto, among other reasons, prevent high intake temperatures that couldpromote pre-ignition (e.g., engine knock). Additional temperaturesensors, pressure sensors, and/or flow sensors may be positioned afterthe EGR valve 76 proximate a charge air stream. Accordingly, dataindicative of the temperature, pressure, and flow of the exhaust gasentering the charge air stream (and, consequently, the intake manifold)can be communicated to the controller 100. Moreover, data indicative ofthe temperature drop as measured by temperature sensors upstream anddownstream of the EGR cooler 74 may be determined and/or approximated.

Although the exhaust aftertreatment system 22 shown includes one of aDOC 30, DPF 40, SCR catalyst 50, and AMOx catalyst 60 positioned inspecific locations relative to each other along the exhaust flow path,in other embodiments the exhaust aftertreatment system may include morethan one of any of the various catalysts positioned in any of variouspositions relative to each other along the exhaust flow path.Additionally, although the DOC 30 and AMOx catalyst 60 are non-selectivecatalysts, in some embodiments, the DOC and AMOx catalyst can beselective catalysts. Further, the EGR system 70 may include other flowpaths, or components not described above.

FIG. 1 is also shown to include an operator input/output (I/O) device120. The operator I/O device 120 is communicably coupled to thecontroller 100, such that information may be exchanged between thecontroller 100 and the I/O device 120. The information exchanged betweenthe controller 100 and the I/O device 120 may relate to one or morecomponents of FIG. 1 or any of the determinations of the controller 100disclosed herein. The operator I/O device 120 enables an operator of thevehicle (or an occupant of the vehicle) to communicate with thecontroller 100 and other components of the vehicle, such as thoseillustrated in FIG. 1. For example, the operator input/output device 120may include an interactive display, a touchscreen device, one or morebuttons and switches, voice command receivers, etc. The controller 100may provide a fault notification (e.g., via the I/O device 120) based onthe determined state of the SCR and AMOx system.

The controller 100 is structured to control the operation of the enginesystem 10 and associated sub-systems, such as the internal combustionengine 20 and the exhaust aftertreatment system 22. According to oneembodiment, the components of FIG. 1 are embodied in a vehicle. Thevehicle may include an on-road or an off-road vehicle including, but notlimited to, line-haul trucks, mid-range trucks (e.g., pick-up trucks),tanks, airplanes, and any other type of vehicle that utilizes an SCRsystem. Communication between and among the components may be via anynumber of wired or wireless connections. For example, a wired connectionmay include a serial cable, a fiber optic cable, a CAT5 cable, or anyother form of wired connection. In comparison, a wireless connection mayinclude the Internet, Wi-Fi, cellular, radio, etc. In one embodiment, acontroller area network (“CAN”) bus provides the exchange of signals,information, and/or data. The CAN bus includes any number of wired andwireless connections. Because the controller 100 is communicably coupledto the systems and components of FIG. 1, the controller 100 isstructured to receive data from one or more of the components shown inFIG. 1. For example, the data may include NOx data (e.g., an incomingNOx amount from NOx sensor 55 and an outgoing NOx amount from NOx sensor57), dosing data (e.g., timing and amount of dosing delivered from doser56), and vehicle operating data (e.g., engine speed, vehicle speed,engine temperature, etc.) received via one or more sensors. As anotherexample, the data may include an input from operator input/output device120. As described more fully herein, using this data, the controller 100diagnoses and controls the SCR, AMOx, and EGR systems while the SCR,AMOx, and EGR systems are being operated. The structure and function ofthe controller 100 is further described in regard to FIG. 2.

As shown in FIG. 2, an example structure for the controller 100 includesa processing circuit 101 including a processor 102, a memory 115, and anaftertreatment circuit system 103. The processor 102 may be implementedas a general-purpose processor, an application specific integratedcircuit (ASIC), one or more field programmable gate arrays (FPGAs), adigital signal processor (DSP), a group of processing components, orother suitable electronic processing components. The memory 115 (e.g.,RAM, ROM, Flash Memory, hard disk storage, etc.) may store data and/orcomputer code for facilitating the various processes described herein.The memory 115 may be communicably connected to the processor 102 andthe aftertreatment circuit system 103 and structured to provide computercode or instructions to the processor 102 for executing the processesdescribed in regard to the controller 100 herein. Moreover, the memory115 may be or include tangible, non-transient volatile memory ornon-volatile memory. Accordingly, the memory 115 may include databasecomponents, object code components, script components, or any other typeof information structure for supporting the various activities andinformation structures described herein.

The example controller 100 further includes a communications interface104 structured to provide communication between the controller 100, theengine 20, the operator input/output device 120, and the aftertreatmentsystem 22. The communications interface 104 may be implemented as aserial bus, a RS232 connection, a wireless router or hub, or anothercommunications interface structure.

The aftertreatment circuit system 103 includes various circuits forcompleting the activities described herein. More particularly, theaftertreatment circuit system 103 includes circuits structured tooperate components of the engine 20 and the aftertreatment system 22.While various circuits with particular functionality are shown in FIG.2, it should be understood that the controller 100, memory 115, andaftertreatment circuit system 103 may include any number of circuits forcompleting the functions described herein and that any number of thecircuits described may be combined into a single circuit. For example,the activities and functionalities of the circuits of the aftertreatmentcircuit system 103 may be embodied in the memory 115, or combined inmultiple circuits or as a single circuit. Additional circuits withadditional functionality may be included. Further, it should beunderstood that the controller 100 may further control other vehicleactivity beyond the scope of the present disclosure.

The aftertreatment circuit system 103 includes an engine circuit 105structured to control the engine 20, a DPF circuit 106 structured tomonitor the operation of the DPF 40, an idle mode circuit 107 structuredto operate the engine 20 in a standard idle mode, a NOx circuit 108 incommunication with the NOx sensors 12, 14, 55, 57, an ammonia circuit109 in communication with sensors associated with the SCR catalyst 50and/or the AMOx catalyst 60, a fuel efficient idle timer circuit 110, afuel efficient idle mode circuit 111 structured to control a fuelefficient idle mode operation of the engine 20, a dosing circuit 112structured to control operation of the DEF source 54, an EGR circuit 113structured to control the EGR system 70, and a notification circuit 114.

The engine circuit 105 is structured to receive information from a user(e.g., via the operator input/output device 120) and to provideinstructions to or otherwise control operation parameters of the engine.The DPF circuit 106 is structured to monitor the aftertreatment system22. For example, the DPF circuit 106 may be structured to monitor anddetermine if the aftertreatment system 22 is undergoing a regenerationprocess and to provide instructions that a regeneration process isrequired. The DPF circuit 106 is in communication with temperaturesensors and is structured to monitor the readings of the temperaturesensors during the regeneration process. In some embodiments, the DPFcircuit 106 can communicate with the engine circuit 105 or othercircuits to maintain a desirable regeneration condition during aregeneration process.

The idle mode circuit 107 is structured to communicate with the enginecircuit 105 and to operate the engine 20 in the standard idle mode. Thestandard idle mode may be one of many different idle arrangementsincluding, for example, a CARB clean idle that meets California'sCommercial Vehicle Idling Regulations, or any other existing idlestrategy. To accomplish the standard idle mode, the idle mode circuit107 may communicate with other circuits, such as the ammonia circuit109, the dosing circuit 112, and the EGR circuit 113 to control theaftertreatment system 22. For example, in one embodiment, the idle modecircuit 107 is structured to communicate with the dosing circuit 112 toprevent the dosing circuit 112 from providing any reactant in response athreshold amount of reactant being present in the SCR catalyst 50.

The NOx circuit 108 is structured to communicate with the NOx sensors12, 14, 55, 57 and provide information regarding NOx levels to the othercircuits of the aftertreatment circuit system 103 and to components ofthe memory 115. The NOx circuit 108 may process raw data received fromthe NOx sensors 12, 14, 55, 57 in addition to other sensor data toprovide information indicative of an NOx level to the other circuits ofthe aftertreatment circuit system 103 and to components of the memory115.

In one embodiment, the ammonia circuit 109 is a stored reductantdetermination circuit that is structured to determine an ammonia storageindication that represents an amount of ammonia stored in the SCRcatalyst 50. The ammonia circuit 109 is structured to communicate withthe dosing circuit 112, the temperature sensors 16, 18, and the NOxsensors 12, 14, 55, 57 to determine the ammonia storage indication. Theammonia circuit 109 is further structured to determine a nitrogen oxideconversion efficiency of the SCR system 52 based at least in part on theNOx levels and the ammonia storage indication.

The fuel efficient idle timer circuit 110 is structured to record a timeor a count in response to directions from one or more circuits of theaftertreatment circuit system 103 or in response to components of thememory 115. In some embodiments, the fuel efficient idle timer circuit110 triggers the fuel efficient idle mode. In some embodiments, the fuelefficient idle timer circuit 110 includes a separate or additional timecomparison circuit for comparing the time value to the time thresholds.

In some embodiments, the fuel efficient idle mode circuit 111 is a typeof fuel mode economy circuit and is structured to communicate with theengine circuit 105 and to operate the engine 20 in a fuel efficient idlemode. The fuel efficient idle mode circuit 111 is also structured tocommunicate with the ammonia circuit 109, the fuel efficient idle timercircuit 110, the dosing circuit 112, and the EGR circuit 113 to operatethe fuel efficient idle mode in response to the ammonia storageindication.

The dosing circuit 112 is structured to provide a dosing command thatadjusts a reductant dosing amount and a timing of a dosing injection. Assuch, the dosing command may be provided to a doser, such as doser 56.The dosing circuit 112 may also communicate with the ammonia circuit 109and the NOx circuit 108, and accumulate dosing data regarding the amountand timing of reductant added to the aftertreatment system 22.

The EGR circuit 113 is structured to communicate with and control theEGR cooler 74 and the EGR valve 76. The EGR circuit 113 is also incommunication with the idle mode circuit 107 and the fuel efficient idlemode circuit 111 and structured to control the EGR valve 76 in responseto commands from the idle mode circuit 107 and the fuel efficient idlemode circuit 111.

The notification circuit 114 is structured to provide one or morenotifications. The notifications may correspond with a fault code, anotification (e.g., on the operator I/O device 120), an idle state ormode, and the like. The notification may indicate the state (e.g.,healthy or degraded, active or inactive) for the SCR and AMOx system andthe EGR system 70.

In general, the circuits of the aftertreatment circuit system 103 andthe components of the memory 115 communicate with the engine system 10to provide improved idle conditions. More specifically, underpredetermined conditions the fuel efficient mode circuit 111 enacts thefuel efficient idle mode and the EGR valve 76 is closed and/or the SCRsystem 52 is inhibited from dosing reductant while still meetingrequired NOx output levels (e.g., according to California's CommercialVehicle Idling Regulations, or any other threshold, standard, oremissions regulation). In one embodiment, the fuel efficient idle modeis enacted based on an SCR bed temperature being above a predeterminedSCR bed temperature threshold. In some embodiments, the NOx sensors willnot wake or otherwise function properly at too low of a SCR bedtemperature. Additionally, at low SCR bed temperatures, the conversionefficiency of the SCR system 52 may be lower than desired. Below, anexample method of operating the engine system 10 is discussed withrespect to FIG. 3. The method discussed with respect to FIG. 3 makesreference to the controller 100, processor 101, and aftertreatmentcircuit system 103, though it should be understood that othercontrollers with alternative structure may be used to implement theprocesses and methods disclosed herein.

Referring now to FIG. 3, a flow diagram of a method 200 of operating anengine system is shown according to an example embodiment. The method200 is initialized at step 202. For example, the method 200 may beinitialized when the engine 20 of the vehicle is started, when acomponent of the SCR system 52 exceeds a threshold temperate, when ameasurement of exhaust gas flowing through the SCR system 52 exceeds athreshold temperature, or in response to another measurement exceedingor falling below a threshold, or anytime that the engine system 10 ispowered (e.g., by a battery).

At step 204, the DPF circuit 106 determines if the engine system 10 isoperating in a regeneration mode. In one embodiment, if the enginesystem 10 is undergoing regeneration, then at step 206 the DPF circuit106 allows the regeneration to continue until the conditions requiringregeneration no longer exist. If the DPF circuit 106 determines at step204 that the engine is not operating in the regeneration mode and thatregeneration is not required, then at step 208 the engine circuit 105determines if the engine 20 is operating at idle. If the DPF circuit 106determines that the engine 20 is not operating at idle, then at step 210the engine circuit 105 communicates with the fuel efficient timercircuit 110 to cause the time value to be set at zero. At step 212, theengine circuit 105 operates the engine 20 according to a user input(e.g., driving, braking, etc.).

At step 208, the engine circuit 105 determines if the engine 20 isoperating at idle. At step 214, in response to the engine circuit 105determining that the engine 20 is operating at idle, the NOx circuit 108communicates with the NOx sensors 12, 14, 55, 57 and determines a NOxvalue. The NOx circuit 108 further compares the NOx value to a NOxthreshold. In some embodiments, the NOx threshold is predetermined. Inone embodiment, the NOx threshold is about thirty grams per hour. Inanother embodiment, the NOx threshold is about twenty-five grams perhour. In yet another embodiment, the NOx threshold is about twenty gramsper hour. However, it will be appreciated that any NOx threshold may beused as the NOx threshold. At step 216, in response to the NOx circuit108 determining that the NOx value is equal to or greater than the NOxthreshold value, the idle mode circuit 107 communicates with the fuelefficient idle timer circuit 110 to set the time value to zero.

After zeroing the time value at step 216, the idle mode circuit 107directs the engine circuit 105 to operate the engine 20 in the standardidle mode at step 218. When the engine 20 is operated in the standardidle mode, the dosing circuit 112 provides commands to the SCR system 52to dose reductant from the DEF source 54 into the exhaust stream, andthe EGR circuit 113 controls the EGR valve 76 to provide recirculatedexhaust gases to the engine 20. In one embodiment, the SCR system 52doses more reductant than a minimum calculated reductant dose in orderto increase the ammonia storage within the SCR system 52. The dosing andrecirculation continue and are controlled to maintain the NOx valuebelow a regulation NOx threshold (e.g., as set by a state or regulatoryagency, thirty grams per hour, twenty grams per hour, any predeterminedvalue). In some embodiments, when the engine 20 is operated in thestandard idle mode, the controller 100 continues to operate according tothe method 200 such that the DPF circuit 106 continues to determine ifthe engine system 10 is operating in a regeneration mode, and so on. Insome embodiments, regeneration may occur at step 206 only while theengine 20 is operating in the standard idle mode.

If the NOx circuit 108 determines that the NOx value is less than theNOx threshold value at step 214, then the fuel efficient idle modecircuit 111 communicates with the ammonia circuit 109 to compare theammonia storage indication to an ammonia storage threshold at step 220.The ammonia storage indication may be based at least in part on amountof DEF dosed by the SCR system 52 over a set time period, and thereadings of the NOx sensors 12, 14, 55, 57 over time. If the ammoniastorage indication is less than or equal to the ammonia storagethreshold, then the method 200 continues to step 216. If the ammoniastorage indication is greater than the ammonia storage threshold, thenthe fuel efficient idle mode circuit 111 communicates with the fuelefficient idle timer circuit 110 and compares the time value to a fuelefficient idle time threshold at step 222. In one embodiment, the fuelefficient idle time threshold is about ten minutes. In anotherembodiment, the fuel efficient idle time threshold is between about tenminutes and about thirty minutes.

If the fuel efficient idle mode circuit 111 determines at step 222 thatthe time value is greater than or equal to the fuel efficient idle timethreshold, then the method 200 continues to step 216 and the engine isoperated in the standard idle mode. If the fuel efficient idle modecircuit 111 determines at step 222 that the time value is less than thefuel efficient idle time threshold, then the fuel efficient idle modecircuit 111 communicates with the engine circuit 105, the DPF circuit106, the dosing circuit 112, and the EGR circuit 113 to operate theengine 20 in the fuel efficient idle mode at step 224. During fuelefficient idle mode, regeneration, DEF dosing, and EGR are inhibited orstopped altogether. In other words, in some embodiments, the DPF circuit106 does not initiate regeneration, the dosing circuit 112 does notcommunicate to the SCR system 52 to dose reductant, and the EGR circuit113 does not direct the opening of the EGR valve 76 when the engine 20is operated in the fuel efficient idle mode.

In some embodiments, during operation of the engine 20 in the fuelefficient idle mode, the fuel efficient idle timer circuit 110increments the time value at step 226, and the method 200 continues. Inthis way, the fuel efficient idle mode will continue until regenerationis needed, the user directs the engine to exit idle, the NOx valueexceeds the NOx threshold, the ammonia storage indication drops belowthe ammonia storage threshold, or the time value exceeds the fuelefficient idle time threshold. Taken together, the data or sensoroutputs and determined values used in the method 200 may be termedoperation data.

The fuel efficient idle mode increases fuel efficiency during operationby reducing or eliminating EGR and/or reductant dosing. In someembodiments, the fuel efficient idle mode includes reducing oreliminating EGR but does not affect reductant dosing. In otherembodiments, the fuel efficient idle mode reduces or eliminatesreductant dosing but does not affect EGR. The reduction or eliminationof EGR and/or reductant dosing increases the fuel efficiency of theengine 20 while continuing operation within the regulated emissionthresholds, so that the user can reduce fuel costs while notsubstantially increasing environmental impact.

It should be understood that no claim element herein is to be construedunder the provisions of 35 U.S.C. § 112(f), unless the element isexpressly recited using the phrase “means for.” The schematic flow chartdiagrams and method schematic diagrams described above are generally setforth as logical flow chart diagrams. As such, the depicted order andlabeled steps are indicative of representative embodiments. Other steps,orderings and methods may be conceived that are equivalent in function,logic, or effect to one or more steps, or portions thereof, of themethods illustrated in the schematic diagrams. Further, referencethroughout this specification to “one embodiment”, “an embodiment”, “anexample embodiment”, or similar language means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the presentinvention. Thus, appearances of the phrases “in one embodiment”, “in anembodiment”, “in an example embodiment”, and similar language throughoutthis specification may, but do not necessarily, all refer to the sameembodiment.

Additionally, the format and symbols employed are provided to explainthe logical steps of the schematic diagrams and are understood not tolimit the scope of the methods illustrated by the diagrams. Althoughvarious arrow types and line types may be employed in the schematicdiagrams, they are understood not to limit the scope of thecorresponding methods. Indeed, some arrows or other connectors may beused to indicate only the logical flow of a method. For instance, anarrow may indicate a waiting or monitoring period of unspecifiedduration between enumerated steps of a depicted method. Additionally,the order in which a particular method occurs may or may not strictlyadhere to the order of the corresponding steps shown. It will also benoted that each block of the block diagrams and/or flowchart diagrams,and combinations of blocks in the block diagrams and/or flowchartdiagrams, can be implemented by special purpose hardware-based systemsthat perform the specified functions or acts, or combinations of specialpurpose hardware and program code.

Many of the functional units described in this specification have beenlabeled as circuits, in order to more particularly emphasize theirimplementation independence. For example, a circuit may be implementedas a hardware circuit comprising custom very-large-scale integration(VLSI) circuits or gate arrays, off-the-shelf semiconductors such aslogic chips, transistors, or other discrete components. A circuit mayalso be implemented in programmable hardware devices such as fieldprogrammable gate arrays, programmable array logic, programmable logicdevices or the like.

As mentioned above, circuits may also be implemented in machine-readablemedium for execution by various types of processors, such as processor102 of FIG. 2. An identified circuit of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions, which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedcircuit need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the circuit and achieve the stated purposefor the circuit. Indeed, a circuit of computer readable program code maybe a single instruction, or many instructions, and may even bedistributed over several different code segments, among differentprograms, and across several memory devices. Similarly, operational datamay be identified and illustrated herein within circuits, and may beembodied in any suitable form and organized within any suitable type ofdata structure. The operational data may be collected as a single dataset, or may be distributed over different locations including overdifferent storage devices, and may exist, at least partially, merely aselectronic signals on a system or network.

The computer readable medium (also referred to herein asmachine-readable media or machine-readable content) may be a tangiblecomputer readable storage medium storing the computer readable programcode. The computer readable storage medium may be, for example, but notlimited to, an electronic, magnetic, optical, electromagnetic, infrared,holographic, micromechanical, or semiconductor system, apparatus, ordevice, or any suitable combination of the foregoing. As alluded toabove, examples of the computer readable storage medium may include butare not limited to a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), a portable compact discread-only memory (CD-ROM), a digital versatile disc (DVD), an opticalstorage device, a magnetic storage device, a holographic storage medium,a micromechanical storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, and/or storecomputer readable program code for use by and/or in connection with aninstruction execution system, apparatus, or device.

The computer readable medium may also be a computer readable signalmedium. A computer readable signal medium may include a propagated datasignal with computer readable program code embodied therein, forexample, in baseband or as part of a carrier wave. Such a propagatedsignal may take any of a variety of forms, including, but not limitedto, electrical, electro-magnetic, magnetic, optical, or any suitablecombination thereof. A computer readable signal medium may be anycomputer readable medium that is not a computer readable storage mediumand that can communicate, propagate, or transport computer readableprogram code for use by or in connection with an instruction executionsystem, apparatus, or device. As also alluded to above, computerreadable program code embodied on a computer readable signal medium maybe transmitted using any appropriate medium, including but not limitedto wireless, wireline, optical fiber cable, Radio Frequency (RF), or thelike, or any suitable combination of the foregoing. In one embodiment,the computer readable medium may comprise a combination of one or morecomputer readable storage mediums and one or more computer readablesignal mediums. For example, computer readable program code may be bothpropagated as an electro-magnetic signal through a fiber optic cable forexecution by a processor and stored on RAM storage device for executionby the processor.

Computer readable program code for carrying out operations for aspectsof the present invention may be written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Java, Smalltalk, C++ or the like and conventionalprocedural programming languages, such as the “C” programming languageor similar programming languages. The computer readable program code mayexecute entirely on the user's computer (such as via the controller 100of FIGS. 1 and 2), partly on the user's computer, as a stand-alonecomputer-readable package, partly on the user's computer and partly on aremote computer or entirely on the remote computer or server. In thelatter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider).

The program code may also be stored in a computer readable medium thatcan direct a computer, other programmable data processing apparatus, orother devices to function in a particular manner, such that theinstructions stored in the computer readable medium produce an articleof manufacture including instructions which implement the function/actspecified in the schematic flowchart diagrams and/or schematic blockdiagrams block or blocks.

Accordingly, the present disclosure may be embodied in other specificforms without departing from its spirit or essential characteristics.The described embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the disclosure is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. An apparatus comprising: a stored reductantdetermination circuit structured to determine an amount of storedreductant in a component of an exhaust aftertreatment system; a fuelmode economy circuit structured to control an amount of reductant addedto the exhaust aftertreatment system during an engine idle mode ofoperation based on the amount of stored reductant.
 2. The apparatus ofclaim 1, wherein the fuel mode economy circuit is further structured tocontrol the amount of reductant added based on operation data regardingexhaust gas flowing through the exhaust aftertreatment system, whereinthe operation data includes an indication of an amount of nitrogen oxideexiting the exhaust aftertreatment system, wherein in response to theamount of nitrogen oxide exiting the exhaust aftertreatment systemexceeding a predetermined threshold, the fuel mode economy circuit isfurther structured to discontinue control of reductant dosing in theexhaust aftertreatment system.
 3. The apparatus of claim 1, wherein thefuel mode economy circuit is further structured to control the amount ofreductant added based on operation data regarding exhaust gas flowingthrough the exhaust aftertreatment system, wherein the operation dataincludes an indication of an amount of nitrogen oxide exiting theexhaust aftertreatment system, wherein the component includes aselective catalytic reduction (SCR) component, and wherein the reductantis urea.
 4. The apparatus of claim 3, wherein the fuel mode economycircuit is structured to determine a nitrogen oxide conversionefficiency of the SCR component based on the stored urea amount and theindication of nitrogen oxide exiting the exhaust aftertreatment system.5. The apparatus of claim 1, wherein the fuel mode economy circuit isfurther structured to control the amount of reductant added based onoperation data regarding exhaust gas flowing through the exhaustaftertreatment system, wherein the operation data includes an indicationof an amount of nitrogen oxide exiting the exhaust aftertreatmentsystem, wherein in response to the amount of nitrogen oxide exiting theexhaust aftertreatment system exceeding a predetermined threshold, thefuel mode economy circuit is further structured to activate an existingengine idle process.
 6. The apparatus of claim 1, wherein the reductantincludes a first reductant and a second reductant, wherein the firstreductant is urea and the second reductant is ammonia.
 7. The apparatusof claim 6, wherein the stored reductant determination circuit isstructured to determine an amount of stored ammonia, and wherein thefuel mode economy circuit is structured to control an amount of ureaadded to the exhaust aftertreatment system during an engine idle mode ofoperation based on the amount of stored amount of ammonia.
 8. Theapparatus of claim 1, further including a timer circuit.
 9. Theapparatus of claim 8, wherein the timer circuit is structured toactivate and maintain activation of the fuel mode economy circuit for apredefined amount of time during the engine idle mode of operation basedon the operation data regarding exhaust gas flowing through the exhaustaftertreatment system.
 10. The apparatus of claim 8, further comprisinga time comparison circuit arranged to compare a time count stored in thetimer circuit to a fuel economy mode time threshold.
 11. The apparatusof claim 1, wherein the fuel mode economy circuit is inhibited fromcontrolling the amount of reductant added if a selective catalyticreduction bed temperature is below a predetermined selective catalyticreduction bed temperature threshold.
 12. The apparatus of claim 1,wherein the fuel mode economy circuit is inhibited from controlling theamount of reductant added if the exhaust aftertreatment system isperforming a regeneration.
 13. A system comprising: an exhaustaftertreatment system including a reductant source and a selectivecatalytic reduction (SCR) component; and a controller in communicationwith the exhaust aftertreatment system, the controller structured to:determine an amount of stored reductant in the SCR component of theexhaust aftertreatment system; and control an amount of reductant addedto the exhaust aftertreatment system during an engine idle mode ofoperation based on the amount of stored reductant.
 14. The system ofclaim 13, wherein the controller is further structured to control theamount of reductant added based on operation data regarding exhaust gasflowing through the exhaust aftertreatment system, wherein the operationdata includes an indication of an amount of nitrogen oxide exiting theexhaust aftertreatment system, wherein in response to the amount ofnitrogen oxide exiting the exhaust aftertreatment system exceeding apredetermined threshold, the controller is further structured toincrease the amount of reductant added to the exhaust aftertreatmentsystem.
 15. The system of claim 13, wherein the controller is furtherstructured to control the amount of reductant added based on operationdata regarding exhaust gas flowing through the exhaust aftertreatmentsystem, wherein the operation data includes an indication of an amountof nitrogen oxide exiting the exhaust aftertreatment system, and whereinthe reductant is urea.
 16. The system of claim 13, wherein thecontroller is structured to control the amount of reductant added to theexhaust aftertreatment system based on operation data regarding exhaustgas flowing through the exhaust aftertreatment system and the storedreductant amount for a predefined amount of time.
 17. A methodcomprising: detecting a level of nitrogen oxide present in a flow ofexhaust gas downstream of a catalyst during an engine idle mode ofoperation; comparing the detected level of nitrogen oxide to athreshold; inhibiting a flow of reductant to the catalyst when thenitrogen oxide level is below the threshold; and providing reductant tothe catalyst when the nitrogen oxide level is above the threshold. 18.The method of claim 17, further comprising determining if an ammonialevel present in the catalyst is above an ammonia storage threshold. 19.The method of claim 17, wherein providing the reductant to the catalystincludes providing substantially more than a minimum calculatedreductant dose.
 20. The method of claim 17, further comprising timing aduration that the flow of reductant to the catalyst is inhibited, andproviding reductant to the catalyst after the duration reaches a timingthreshold.
 21. The method of claim 20, wherein the timing threshold isbetween about ten minutes and about thirty minutes.
 22. The method ofclaim 17, further comprising operating an exhaust gas recirculationsystem when the nitrogen oxide level is above the threshold, andinhibiting operation of the exhaust gas recirculation system when thenitrogen oxide level is below the threshold.